CN201072456Y - Four-port circulator - Google Patents

Abstract

The utility model relates to a four-port circulator used in fiber communication, which is characterized by simple structure, small volume, low cost, excellent performance parameters, etc. The utility model comprises the components: first focusing lens, a first polarized light analyzer crystal, a first half-wave plate, a Faraday rotator, a first wedge-shaped plate, a second wedge-shaped plate, a second Faraday rotator, a second half-wave plate, a second polarized light analyzer crystal, second focusing lens, a compensating plate and a magnetic ring. The first wedge-shaped plate, the first Faraday rotator, the second wedge-shaped plate and the second Faraday rotator are arranged along the direction of a longitudinal axle in sequence. Along the direction of the longitudinal axle of the four-port circulator, the compensating plate is arranged between the second Faraday rotator and the second polarized light analyzer crystal and is parallel with a optical path passing through the second half-wave plate as well as being arranged at another optical path outside the second half-wave plate. A medial axle of the magnetic ring is parallel with the direction of the longitudinal axle.

Description

Four Port Circulator

technical field

The utility model relates to a circulator used for optical fiber communication, especially a four-port circulator, which couples the light beam transmitted from the first optical fiber to the second optical fiber, and couples the light beam transmitted from the second optical fiber to the third optical fiber. The optical fiber couples the beam from the third optical fiber to the fourth optical fiber.

Background technique

With the continuous development of optical communication technology, optical circulators, as an important component of passive devices, are more and more widely used in system design and equipment manufacturing. It can be used in the dispersion compensation system to compensate the dispersion generated in the transmission process of the high-speed optical fiber transmission system. It can also be widely used in two-way communication, optical wavelength upload and download, and can also be used as add-drop multiplexing equipment, etc.

An optical circulator is a non-reciprocal device that transmits light sequentially in one direction. For a circulator with n ports, the optical signal input from the i-th (i=1, 2, ... n-1) port can only be output from the i+1-th port. In an ideal circulator, the optical signal injected into the nth port can only be output from the first port. However, in the actual application of the optical circulator, the state that the end optical signal is output by the head end has no practical significance in actual use, so it is generally unnecessary. Considering the manufacturing process and practical application environment of optical circulators, three-port and four-port circulators are the two most widely used.

At present, a commonly used four-port circulator generally includes three functional modules, namely a first optical function combination block, a second optical function combination block and a third optical function combination block.

The first optical function combination block is an optical element combination block that realizes the functions of laser input and output, polarization splitting and combining, and polarization rotation. It mainly consists of a double fiber optic head, a focusing lens, a deflecting optical device, a polarization splitting crystal, two half-wave plate assemblies and a Faraday rotator. The two optical fibers of the dual optical fiber head correspond to the first port and the second port of the circulator respectively.

The function and principle of the third optical function combination block are the same as those of the first optical function combination block, and the structure is also similar. The two optical fibers of the dual optical fiber head correspond to the third port and the fourth port of the circulator respectively.

The second optical function combination block mainly includes a polarized light splitting device. The laser light incident from the first port passes through the first optical functional combination block and rotates the polarization direction, and then enters the polarized light splitting device of the second optical functional combination block, which corresponds to ordinary light. The beam passes straight through, and then passes through the second optical functional combination block. After the three optical function combination blocks rotate the polarization direction and combine the light, it is coupled to the second port and output. In the same way as this, the laser light injected from the third port is output from the fourth port. The laser light injected from the second port passes through the third optical functional combination block, which is polarized and split and rotated, and then enters the polarized light splitting device of the second optical functional combination block, which corresponds to extraordinary light. The beam is translated when it exits, and then After the first optical function combination block rotates the polarization direction and combines the light, it is coupled to the third port and output.

The components of the above-mentioned part of the circulator, the Faraday rotator, are usually made of permanent magnetic materials. If it encounters a strong magnetic field environment, this Faraday rotator will produce demagnetization; and if the magnetic field strength is insufficient, because the Faraday rotator needs to be under the action of a certain strength magnetic field to achieve the optical rotation effect at a certain angle, the optical rotation angle will not be reached. to request. In addition, the above-mentioned four-port circulator has a rather complex structure, a large volume, high manufacturing cost, low manufacturing efficiency, and unstable performance parameters.

Utility model content

The purpose of the utility model is to provide a four-port circulator. The circulator has the advantages of simple structure, small volume, low manufacturing cost and high production efficiency.

According to the four-port circulator designed according to the above purpose, the first optical fiber and the third optical fiber of the constituent parts are placed adjacently and side by side along the longitudinal axis of the four-port circulator at one end of the four-port circulator, and are symmetrical to the central plane, The second optical fiber and the fourth optical fiber of its components are placed adjacently side by side along the longitudinal axis of the four-port circulator at the other end of the four-port circulator, and are located opposite the first optical fiber and the third optical fiber, and are symmetrical on the central plane. The four-port circulator includes the following elements: a first focusing lens, a first polarizing beam splitting crystal, a first half-wave plate, a first Faraday rotator, a first angle wedge plate, a second angle wedge plate, and a second Faraday rotator , a second half-wave plate, a second polarizing beam splitting crystal, a second focusing lens, a compensation plate and a magnetic ring. The first wedge piece, the first Faraday rotator, the second wedge piece, and the second Faraday rotator are arranged in sequence along the longitudinal axis of the four-port circulator. Along the longitudinal axis of the four-port circulator, the compensation plate is located between the second Faraday rotator and the second polarization splitting crystal, which is parallel to the optical path passing through the second half-wave plate and is located outside the second half-wave plate. on the light path. The central axis of the magnetic ring is parallel to the direction of the longitudinal axis.

Generally, in the aforementioned four-port circulator, the first wedge piece, the first Faraday rotator, the second wedge piece, and the second Faraday rotator are simultaneously located in the inner ring of the magnetic ring.

Preferably, in the aforementioned four-port circulator, the included angle between the optical axis and the central plane of the first angle wedge is selected to be 90 degrees, and the included angle between the optical axis and the central plane of the second angled wedge is selected to be 45 degrees.

The above-mentioned focusing lens is a self-focusing lens or a spherical lens. Polarized light splitting crystals are made of birefringent crystal materials. Corner wedges are also made from birefringent crystal materials.

The four-port circulator of the present utility model utilizes the construction method of a Faraday rotator clamped by two wedge angle pieces placed in the inner ring of the magnetic ring, which can realize the combination of multiple devices in the traditional structure. Angle matching tasks, so as to overcome the shortcomings of replacing the traditional structure with bulky volume and long optical path, and become a new product structure with progressively improved technical performance. At the same time, this design simplifies the product structure, reduces the volume of the product, reduces its production cost and improves the production efficiency. In addition, the physical parameters of the four-port circulator with this structure tend to be optimally matched, which greatly improves the technical performance of the product and can be comparable to the current three-port circulator.

Illustration

Fig. 1 is a schematic plan view of the four-port circulator of the present invention.

Fig. 2 is a side view of the optical path of light propagating from the first optical fiber to the second optical fiber in the four-port circulator of the present invention.

Fig. 3 is a side view of the optical path of light propagating from the second optical fiber to the third optical fiber in the four-port circulator of the present invention.

Fig. 4 is a side view of the optical path of light propagating from the third optical fiber to the fourth optical fiber in the four-port circulator of the present invention.

Fig. 5 is a top view of the optical path of light propagating from the first optical fiber to the second optical fiber in the four-port circulator of the present invention.

Fig. 6 is a schematic diagram of an assembly structure of an implementation example of a four-port circulator of the present invention.

Fig. 7 is a schematic diagram of the structure of the wedge angle piece in the implementation example of the four-port circulator of the present invention.

The structural features or component names corresponding to the marks in the figure are as follows, 1~the first capillary, 2~the first focusing lens, 3~the first polarizing beam splitting crystal, 4~the first half-wave plate, 5~the first angle wedge plate , 6~the first Faraday rotator, 7~the second wedge angle plate, 8~the second Faraday rotator, 9~the second half-wave plate, 10~the second polarizing beam splitting crystal, 11~the second focusing lens, 12 ～Second capillary, 13～Compensation sheet, 14～Magnetic ring, a1～First optical fiber, a2～Second optical fiber, a3～Third optical fiber, a4～Fourth optical fiber, p～Central plane, 100～ Four port circulator.

Detailed ways

The four-port circulator of the present utility model will be described in detail below in conjunction with the accompanying drawings.

Figures 1 to 7 are schematic diagrams showing the relevant structures of specific embodiments of the four-port circulator of the present invention.

Referring to Figures 1 and 6, and in combination with Figures 2, 3, and 4, according to the optical tasks undertaken by each component or component combination, the four-port circulator 100 can be regarded as including three functional blocks, that is, the first optical Functional combination block A, second optical function combination block B and third optical function combination block C. The first optical function assembly block A, the second optical function assembly block B and the third optical function assembly block C are combined in the manner described below and then packaged as a whole in the housing 18 shown in FIG. 6 .

Wherein, the first optical function combination block A includes a first capillary 1 , a first focusing lens 2 , a first polarizing beam splitting crystal 3 , and a first half-wave plate 4 .

The second optical function combination block B includes a first wedge 5 , a first Faraday rotator 6 , a second wedge 7 , a second Faraday rotator 8 , and a magnetic ring 14 .

The third optical function combination block C includes a second half-wave plate 9 , a second polarization splitting crystal 10 , a second focusing lens 11 , a second capillary 12 , and a compensation plate 13 .

The first capillary 1 is covered with a first optical fiber a1 and a third optical fiber a3. Along the longitudinal axis of the four-port circulator 100, that is, the z-axis direction of the Cartesian coordinate system oxyz shown in FIG. , and the two optical fibers a1, a3 are symmetrical to the central plane p of the four-port circulator 100 . The second capillary 12 is coated with a second optical fiber a2 and a fourth optical fiber a4. Along the longitudinal axis of the four-port circulator 100, that is, the z-axis direction of the Cartesian coordinate system oxyz shown in FIG. , that is, located opposite to the first optical fiber a1 and the third optical fiber a3, and the two optical fibers a2, a4 are also symmetrical to the central plane p. The central plane p is the central axis of the optical component, that is, the z-axis of the rectangular coordinate system oxyz shown in Figure 1, and the plane formed by the first optical fiber a1 and the third optical fiber a3, which is parallel to the rectangular coordinate system oxyz shown in Figure 1 yoz plane.

The first focusing lens 2 is a collimator, which can respectively focus and collimate the light rays corresponding to the first optical fiber a1 and the third optical fiber a3 into the first beam of parallel light L1 (as shown in FIG. 2 ) and the second beam of parallel light. The three beams of parallel light L3 (as shown in FIG. 4 ) can also lead the second beam of parallel light L2 (as shown in FIG. 3 ) correspondingly from the second optical fiber a2 into the third optical fiber a3.

The second focusing lens 11 is also a collimator, and its function is similar to that of the first focusing lens 2. It can introduce the first bundle of parallel light L1 correspondingly from the first optical fiber a1 into the second optical fiber a2, and can also guide the corresponding The light in the second optical fiber a2 is collimated into a second beam of parallel light L2.

Both the first polarized light splitting crystal 3 and the second polarized light splitting crystal 10 are birefringent crystals, and their functions are to convert parallel light into components with mutually perpendicular polarization states and synthesize the components with mutually perpendicular polarization states into parallel light .

The first half-wave plate 4 and the second half-wave plate 9 rotate the vibration direction of the polarized light passing through them by 90 degrees.

The compensation sheet 13 is used for compensating the optical path difference of the two beams of light separated by the polarization beam splitting crystal. Along the longitudinal axis direction of the four-port circulator 100, the position of the compensation plate 13 is between the second Faraday rotator 8 and the second polarization splitting crystal 10, parallel to the optical path passing through the second half-wave plate 9 and located at the first Another optical path other than the second half-wave plate 9. Preferably, it is on the same cross-section as that of the second half-wave plate 9 .

The magnetic ring 14 is a permanent magnet, which is used to provide a magnetic field for the first Faraday rotator 6 and the second Faraday rotator 8 .

The combination of the first angle wedge piece 5 and the second angle wedge piece 7 can deflect the light emitted from the second optical fiber a2 by an angle so that it enters the third optical fiber a3.

Both the first Faraday rotator 6 and the second Faraday rotator 8 are polarization rotators, and their function is to change the polarization state of the light from perpendicular to parallel or from parallel to perpendicular.

Along the longitudinal axis of the four-port circulator 100 , the first angled wedge 5 , the first Faraday rotator 6 , the second angled wedge 7 , and the second Faraday rotator 8 are arranged in the order described here.

In the Cartesian coordinate system oxyz shown in Figures 1 and 7, the angle between the optical axis 501 of the first wedge 5 and the central plane p of the four-port circulator 100 is 90 degrees, and the optical axis 701 of the second wedge 7 The included angle with the central plane p of the four-port circulator 100 is 45 degrees.

Referring to Fig. 2 and Fig. 5, the side view and the top view of the optical path of light propagating from the first optical fiber a1 to the second optical fiber a2. The laser light incident from the first optical fiber a1 is collimated by the first focusing lens 2 and becomes the first beam of parallel light L1. After the first beam of parallel light L1 enters the first polarizing beam splitting crystal 3 along the optical path 15, it is split into two paths of polarized light with mutually perpendicular polarization states, namely ordinary light L1a and extraordinary light L1b (see FIG. 5 ). The ordinary light L1a passes through the first half-wave plate 4 with an optical axis direction of 45 degrees, and the polarization direction of the light is rotated by 90 degrees to obtain the same polarization direction as the extraordinary light L1b. Subsequently, the two beams of light L1a and L1b with the same polarization direction respectively pass through the first corner wedge 5 of the Wollaston prism. When the two beams of light L1a and L1b with the same polarization direction pass through the first corner wedge 5 , the vibration direction remains unchanged. In terms of the relationship between its vibration direction and the optical axis 501 of the first angle wedge 5, with respect to the optical axis 501 (see Figure 7) of the first angle wedge 5, the two light rays L1a and L1b are all ordinary rays . Next, the two beams of light L1a and L1b with the same polarization direction respectively pass through the first Faraday rotator 6 , and their vibration directions are rotated by 45 degrees in the same direction to keep consistent. Then, the two beams of light L1a and L1b with the same polarization direction respectively pass through the second angle wedge 7 of the Wollaston prism, and then pass through the second Faraday rotator 8 to rotate the polarization directions of the two beams of light L1a and L1b in the same direction again by 45 degrees And stay consistent. Similarly, with respect to the second angle wedge 7 and the second Faraday rotator 8, the two beams of light L1a and L1b are also ordinary light. Then, let one beam of polarized light L1a or L1b pass through the second half-wave plate 9 to rotate the polarization direction of this beam of light by 90 degrees. At this time, the vibration directions of the two beams of polarized light L1a and L1b are perpendicular to each other. Finally, let the two beams of light L1a and L1b whose polarization directions are perpendicular to each other enter the second polarization beam splitting crystal 10, synthesize them into a beam of light L1`, and then couple them into the second optical fiber a2 through the second focusing lens 11 . In FIG. 2 , the sectional view corresponding to each optical device on the propagation path of the laser beam clearly shows the polarization state of the two beams of polarized light L1a and L1b after passing through each optical element.

Referring to FIG. 3 , it is a side view of the light path from the second optical fiber a2 to the third optical fiber a3 . The laser light incident from the second optical fiber a2 is collimated by the second focusing lens 11 and becomes a second beam of parallel light L2. The second beam of parallel light L2 enters the second polarizing beam splitting crystal 10 along the optical path 16 and is split into two paths of polarized light with mutually perpendicular polarization states, ie ordinary light L2a and extraordinary light L2b. With reference to the process of the light rays described above in FIG. 2 propagating from the first optical fiber a1 to the second optical fiber a2, when the ordinary light L2a and the extraordinary light L2b reach the second angle wedge piece 7, due to the The rotation angle produced by the second Faraday rotator 8 to polarized light has nothing to do with the incident direction, so relative to the state when the incident laser light from the first optical fiber a1 reaches the second angle wedge plate 7, the ordinary light L2a and the extraordinary light The polarization directions of L2b are both rotated by 90 degrees, and at this time, the two beams of light are both extraordinary lights relative to the second angle wedge plate 7 . Subsequently, after being rotated by the first Faraday rotator 6 for 45 degrees, the vibration direction of the two beams of light L2a, L2b with the same polarization direction is the same as that described in Figure 2 when the light is transmitted from the first optical fiber a1 to the second optical fiber a2. same. Then, the two beams of polarized light L2a, L2b enter the first angle wedge plate 5 and transform into ordinary light. Due to the difference in refractive index between ordinary light and extraordinary light, the light is deflected, and then passes through the first half-wave plate 4, so that the vibration directions of the two beams of polarized light L2a and L2b become perpendicular to each other. Afterwards, after being combined by the first polarizing beam splitting crystal 3, the two beams of light L2a, L2b are combined into one beam of light L2'. Finally, the light beam L2' is coupled into the third optical fiber a3 through the first focusing lens 2 and delivered to the subsequent load. In FIG. 3 , the sectional view corresponding to each optical device on the propagation optical path of the laser beam clearly shows the polarization state of the two beams of polarized light L2a, L2b after passing through each optical element.

Referring to FIG. 4 , it is a side view of the optical path of light propagating from the third optical fiber a3 to the fourth optical fiber a4 . In the state where the light comes from the third optical fiber a3, its propagation mode and coupling transfer condition along the optical path 17 are similar to the process of light propagating from the first optical fiber a1 to the second optical fiber a2 described in FIG. The fourth fiber a4 is used for output to subsequent loads. In FIG. 4 , the cross-sectional view corresponding to each optical device on the propagation optical path of the laser beam clearly shows the polarization state of the two beams of polarized light after passing through each optical element.

Claims (3)

1. A four-port circulator, the first optical fiber and the third optical fiber of its components are placed adjacently side by side along the longitudinal axis of the four-port circulator at one end of the four-port circulator and are symmetrical to the central plane, Its components, the second optical fiber and the fourth optical fiber, are arranged adjacently side by side along the longitudinal axis of the four-port circulator at the other end of the four-port circulator and between the first optical fiber and the first optical fiber. The three optical fibers are opposite and symmetrical to the central plane, and the four-port circulator includes the following elements: the first focusing lens, the first polarizing beam splitting crystal, the first half-wave plate, the first Faraday rotator, and the first wedge angle plate, a second wedge angle plate, a second Faraday rotator, a second half-wave plate, a second polarizing beam splitting crystal, and a second focusing lens, and is characterized in that it also includes: a compensation plate and a magnetic ring, and the first wedge angle sheet, the first Faraday rotator, the second wedge angle sheet, and the second Faraday rotator are arranged in sequence along the longitudinal axis of the four-port circulator, and the compensation sheet is arranged along the four-port annular The direction of the longitudinal axis of the device is located between the second Faraday rotator and the second polarization splitting crystal, which is parallel to the optical path passing through the second half-wave plate and is located outside the second half-wave plate. On the optical path, the central axis of the magnetic ring is parallel to the longitudinal axis of the four-port circulator. 2. The four-port circulator according to claim 1, characterized in that the first wedge, the first Faraday rotator, the second wedge, and the second Faraday rotator are located at the same time In the inner ring of the magnetic ring. 3. The four-port circulator according to claim 1 or 2, characterized in that the angle between the optical axis of the first angle wedge piece and the central plane is 90 degrees, and the optical axis of the second angle wedge piece The included angle between the axis and the central plane is 45 degrees.

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